Health systems interventions for hypertension management and associated outcomes in Sub-Saharan Africa: A systematic review

Hypertension is a significant global health problem, particularly in Sub-Saharan Africa (SSA). Despite the effectiveness of medications and lifestyle interventions in reducing blood pressure, shortfalls across health systems continue to impede progress in achieving optimal hypertension control rates. The current review explores the health system interventions on hypertension management and associated outcomes in SSA. The World Health Organization health systems framework guided the literature search and discussion of findings. We searched PubMed, CINAHL, and Embase databases for studies published between January 2010 and October 2022 and followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We assessed studies for the risk of bias using the tools from the Joanna Briggs Institute. Twelve studies clustered in 8 SSA countries met the inclusion criteria. Two thirds (8/12) of the included studies had low risk of bias. Most interventions focused on health workforce factors such as providers’ knowledge and task shifting of hypertension care to unconventional health professionals (n = 10). Other health systems interventions addressed the supply and availability of medical products and technology (n = 5) and health information systems (n = 5); while fewer interventions sought to improve financing (n = 3), service delivery (n = 1), and leadership and governance (n = 1) aspects of the health systems. Health systems interventions showed varied effects on blood pressure outcomes but interventions targeting multiple aspects of health systems were likely associated with improved blood pressure outcomes. The general limitations of the overall body of literature was that studies were likely small, with short duration, and underpowered. In conclusion, the literature on health systems internventions addressing hypertension care are limited in quantity and quality. Future studies that are adequately powered should test the effect of multi-faceted health system interventions on hypertension outcomes with a special focus on financing, leadership and governance, and service delivery interventions since these aspects were least explored.

Introduction examined the use of patient registries and patient-to-provider and provider-to-provider information sharing in patient management.
Financing. The financing aspect of the health systems, as defined in the WHO building blocks, has the most significant relevance on the national macro-level health systems yet plays an impact on the micro-level health systems' service delivery and patients' outcomes. In the current context, we considered the interventions which evaluated the injection of money into the health systems through health insurance premiums, reduction of the patients' out-ofpocket spending, or funding for hypertension management activities at the health facilities.
Leadership and governance. Leadership and governance have direct and indirect associations with the other five building blocks of the health systems. In this review, we considered an intervention to target leadership and governance if it promoted leadership awareness of the rising burden of hypertension, used strategic planning or implementation of national strategy around hypertension management activities, explored the accountability measures at the health facility, applied regular performance appraisal and planning for improvement, integrated supportive mentorship to low health system level health facilities, instituted a patient feedback collection and response system, or studied the leadership allocation and reallocation of funds for hypertension management. We also considered interventions around leadership joining collaborations (with other health facilities or local/international/national/private organizations) to manage hypertension.
Risk of bias assessment. We used the Joanna Briggs Institute (JBI) tools to assess the quality aspects of the methods and conduct of the studies included in the review [24]. We evaluated the one intervention that utilized a quality improvement strategy using the Standards for Quality Improvement Reporting Excellence 2.0 (SQUIRES) guideline [25]. SQUIRES uses a checklist of standard elements for reports of system-level projects to improve healthcare quality. Two investigators independently assessed the risk of bias for each study, and the third resolved conflicts. The JBI tool uses "Yes," "No," and "Unclear or Not applicable" to assess the different features of study design and the overall appraisal as include study, exclude study, or seek more information. We replaced "Yes," "No," and "Unclear" with "Low risk of bias," high risk of bias," and "Some concerns," respectively, for each statement on the JBI tool. We assigned the overall quality appraisal of each study as "good," "fair," and "poor" and studies with poor quality were excluded. We used the robvis [26] online tool to create risk-of-bias plots where the overall appraisal was also converted to "low risk of bias" for the study of good quality, "some concerns" for studies of fair quality and "high risk of bias" for studies of poor quality.
Analysis and synthesis of findings. After the data extraction, we identified the health systems factors addressed by the interventions for hypertension care. We classified the outcomes of each study into the appropriate group: hypertension awareness, systolic and diastolic BP, treatment initiation and adherence, and BP control. We tracked the reported effect(s) of interventions on hypertension outcomes and compared findings across the different countries of SSA.

Results
We identified 7,494 studies and 3,121 were duplicates (Fig 1). We conducted title and abstract screening for 4,373 studies yielding 205 for full-text review. The latter led to 12 studies for inclusion in this systematic review (Table 1). Of the 12 included studies, six were randomized controlled trials conducted in South Africa (n = 2) [27, 28], Cameroon (n = 1) [29], Ghana (n = 1) [30], Kenya and Uganda (n = 1) [31], and Zambia (n = 1) [32]. Six quasi-experimental studies were conducted in Nigeria (n = 2) [33,34], Botswana (n = 1) [35], Cameroon (n = 1) [36], Kenya (n = 1) [37], and Sierra Leone (n = 1) [38]. The geographic representation of included studies by country is demonstrated in Fig 2. The quality assessment demonstrated a low risk of bias in 67% (8/12) of the included studies (S1 Fig & S2 Table). Among randomized controlled trials, the most common issues were the lack of: concealed intervention allocation, similarity of groups at baseline, and blinding participants and those delivering the intervention about the group (intervention or control groups) assignments. Though it is not feasible to conceal intervention allocation nor to blind participants or interventionists in such health system interventions, the adequate description of the reason for omitting standard procedures of a study design is desirable.

Health system factors and interventions explored
The health system factor that most interventions targeted is the health workforce, followed by interventions to address equipment and medicines, information systems, financing, service delivery, and leadership and governance ( Table 2). The detailed findings from included papers can be found in Table 3.
1. Service delivery. Only one study conducted in Kenya and Uganda addressed the service delivery aspect of the health systems on hypertension care [31]. The study explored the cross-   32,34,[36][37][38]. All ten interventions trained healthcare providers on hypertension treatment guidelines, and seven of them integrated task-shifting strategy [28, 30-32, 34, 36, 38]. Some examples of task-shifting strategy studied are training and giving roles to lay community health workers in South Africa [28] and Zambia [32] to measure BP, having nurses in Cameroon [36] and Ghana [30] and pharmacists in Nigeria [34] to treat hypertension (including assignment of diagnosis and prescribing medications).
Generally, studies that included interventions for the health workforce reported improvement in hypertension outcomes. Improvement in the healthcare providers' skills and knowledge of the correct BP measurement techniques and hypertension diagnosis and treatment, respectively, likely contributed to improved hypertension outcomes in Kenya [37]. In its first year, the program screened 532 527 individuals, diagnosed almost 10% with hypertension, and initiated 72% of those diagnosed on treatment [37].
The impact of task-shifting varied across studies but bent towards positive BP outcomes. In Ghana [30] and Cameroon [36], task-shifting contributed to the significant decline in systolic and diastolic BP but not in the achievement of controlled BP [30,36]. On the other hand, in the two quasi-experimental studies conducted in Nigeria and Zambia, respectively, the taskshifting contributed to the achievement of controlled BP in Nigeria (AOR 2.27, p: 0.049) from baseline to end line and in Zambia from 13% at baseline to 25% (no p-value reported) among patients who attended at least two follow up visits [32,34]. In a cluster randomized controlled trial conducted in South Africa, the task-shifting to lay community health workers in BP measurement and documentation contributed to higher adherence to appointments (75% vs. 56% patients attending their assigned appointments) but no statistically significant improvements in achieving BP control comparing the intervention to the control groups [28]. https://doi.org/10.1371/journal.pgph.0001794.g002

Medical products and technologies.
Almost half (5/12) of the included studies explored the availability of equipment and consumables involved in hypertension management and the associated care outcomes [32,[35][36][37][38]. The procurement of drugs and consumables and improvement in the supply chain implemented in the experimental studies and quality improvement project was in combination with other interventions such as providers' training in Cameroon, Kenya, and Zambia [32,36,37], and better data management in Botswana [35]. In these studies, the impact of the equipment and supply chain was not necessarily isolated but contributed to the overall improvements in BP outcomes.

Health information systems.
Five of the twelve studies evaluated some aspects of health information system interventions on hypertension outcomes [27,29,32,34,35]. The most common forms of health information system interventions involved patient data recording and analysis for quality improvement [27, 32,35] and utilization of technology to facilitate patient-provider or provider-provider information exchange for better hypertension outcomes among patients [29,34]. All interventions that integrated a health information system component demonstrated improved hypertension outcomes except for one randomized controlled trial in South Africa, where hypertension outcomes worsened [27]. In this study, providers reported feeling overwhelmed by the new patient data recording system. 5. Financing. Three studies conducted in Ghana and Nigeria explored the interventions around financing to improve hypertension outcomes[30, 33,34]. In two studies, the financing was directed towards funding the patients' health insurance premiums in Ghana and Nigeria, respectively [30,33], while the third study funded performance-based financial incentives to the clinicians who were consulting patients with hypertension in Nigeria [34]. The one quasiexperimental study that provided health insurance coverage to the intervention group reported no change in hypertension awareness, adherence to treatment, or controlled BP [33]. A randomized controlled trial in Nigeria that provided health insurance coverage to both the intervention and control groups reported a decline in systolic and diastolic BP in both study arms, with a significant and sharper decline in the intervention arm even though the achievement of BP control was not significantly different in the intervention versus control arms.
The incentivization of clinicians who manage patients with hypertension contributed to a 66% achievement of BP control among patients even though there was no data for the control group [34].
6. Leadership and governance. While leadership and governance contribute directly or indirectly to all the above health system factors, studies targeting leadership and governance were scarce. A single quasi-experimental study conducted in Sierra Leone explored one aspect  (1) Health workforce 10 South Africa (2), Kenya and Uganda (1), Cameroon (2), Nigeria (1), Financing 3 Ghana (1), Nigeria (2) Leadership & Governance 1 Sierra Leonne (1) Note: Some studies reported more than one system factor https://doi.org/10.1371/journal.pgph.0001794.t002 of leadership and governance-the collaborations with government and non-government, local and international organizations to train the trainers of hypertension care. The consortium provided training to the providers at the referral health facilities who, in turn, trained and gave supportive mentorship to the health facilities in the lower levels of the health system [38]. This intervention showed a significant reduction in diastolic (from 98 to 86 mmHg, t: 4.069, p: 0.001) but not systolic BP.
Interventions targeting multiple health systems factors. The health systems interventions on hypertension targeted two or more health system components in ten of the twelve studies included. The health workforce and health information systems were the most common combination of factors targeted, followed by the health workforce and medical products. One randomized controlled trial and one quasi-experimental study which targeted a single health system factor, health workforce, and health financing, respectively, did not yield a significant improvement in hypertension outcomes. In contrast, studies which targeted multiple health system factors were likely to demonstrate significant improvements in hypertension outcomes.

Discussion
This systematic review assessed the health system interventions for hypertension awareness, initiation and adherence to hypertension treatment, and achievement of BP control in SSA. Our main findings are that studies to address health systems challenges of hypertension care are very limited in quality and number. The studies we identified addressed mostly the health workforce challenges, access to equipment and medicines, and health information systems. The studies addressing hypertension care delivery issues, such as decentralization of hypertension care and integration delivery, leadership and governance, and financing aspects of the health systems, were minimal. Overall, we found that interventions targeting multiple aspects of the health systems were more likely to show significant improvements in hypertension outcomes than interventions targeting solo health system components.
The healthcare provider's knowledge and adherence to hypertension treatment guidelines stood out as one of the most studied health system interventions on hypertension [37,39,40]. The capacity building among healthcare providers and the task sharing and shifting of hypertension management roles to vital professionals like nurses, pharmacists, and community health workers align with scientific evidence from developing and developed countries [41,42]. For instance, the nurses' role in managing hypertension has evolved from merely measuring and monitoring BP to collaboratively detecting, diagnosing, and referring patients with hypertension and its complications [43,44]. In many countries and settings, nurses prescribe or dispense anti-hypertensive medications, provide patient education and counseling to ensure medication adherence, and assume leadership roles in spearheading quality improvement projects for better management of hypertension [43]. An estimation of the global gap in clinic visits for hypertension care reported that 50% of LMICs and 86% of lower-income countries have a physician deficit even if patients were to make only three annual visits to the health facilities for their hypertension [45]. Neupane and colleagues recommend shifting some hypertension management tasks to non-physician clinicians to bridge that gap [45]. Interdisciplinary collaboration is the way forward for SSA to provide quality hypertension care to patients; however, regional and national policies must align with and support this practice. The second health system component widely explored is the supply of essential medical products, including BP measurement devices and anti-hypertensive medications. It is intuitive to formulate the association between the availability of medical products and hypertension outcomes, yet the challenges that lead to the disruption in the supply chain of medical products are a complex issue to disentangle. The common approach addressed by the interventions was to procure the needed equipment and medications but not to fix the inherent challenges in the availability of those medical products and the supply chain-or attempt to identify loopholes in the process to recommend viable and context-specific solutions. A separate narrative synthesis has identified multiple challenges to the availability of medical products in Africa [46]. The challenges identified include limited pharmaceutical industrial power and high costs of raw materials, overdependence on developed countries for these products, poor supply chain systems, poor government financing, and lack of investment in supply chain research [46]. Unless studies work to identify and address the root cause of the inadequate supply of medical products, short-term solutions are unsustainable and unhelpful in the rising healthcare needs.
WHO defines health information systems as collecting, storing, analyzing, and utilizing patient and healthcare delivery data to improve quality, research, and inform policy [22]. "If you can't measure it, you can't improve it" is a quote often attributed to Peter Drucker about the critical need for a system to continuously collect data and measure what you are trying to improve. The studies we included in the current review examined mainly the patient data collection and sharing between providers and between providers and the patients to improve hypertension outcomes. In many developed countries, health information systems have gone to incorporate technology that has rendered data generation, processing, analysis, visualization, and sharing seamless and less burdensome [47]. One major challenge and critique of health information systems in developed countries is the lack of unification of health information systems across healthcare organizations [47]. Countries in SSA and other developing countries can learn from developed countries and build their health information infrastructure in a unified framework to facilitate patient follow-up outside and across the health facilities, expedite health data reporting, and promote research to advance evidence-based practice, funding allocation, and policy. The health information system interventions identified in the current review did not find studies exploring patient registries to prevent loss to follow-up in hypertension management.
The cross-integration of hypertension services is a service delivery system-level intervention explored for managing hypertension. The advocacy for integrating hypertension and HIV care originated from the realization that many patients with HIV were presenting with hypertension and other non-communicable chronic conditions such as diabetes. HIV care outcomes [48,49]. Sierra Leone [50], South Africa [51], Tanzania and Uganda [52], and Malawi [53] have reported outcomes of some form of HIV and hypertension care integration from the national reports and cohort studies. In those studies and reports, patients demonstrated improved HIV and hypertension outcomes. There are some reasons why taking lessons from the management of chronic infectious diseases could be effective in hypertension care. The management of chronic infectious diseases, HIV and Tuberculosis, in resource-constrained settings has, despite still-existing challenges, produced strong evidence and effective strategies for managing patients with such complicated chronic health conditions amid, just to name a few; insufficient healthcare professionals [54], inaccessibility of health services [55], and poor information management systems [56]. In addition to demonstrating that task sharing with and task shifting to non-physician healthcare providers is possible and effective [54,57,58], the process of managing HIV and Tuberculosis has also demonstrated ways to manage loss to follow up by the use of strong information management systems [56], decentralization of services (another form of delivery system design) close to the community [59], and collaboration with community health workers [54,58]; all the strategies that could be well adapted to hypertension management. One of the information management system strategies that have been effective in HIV and Tuberculosis control and hypertension management in other low-income countries is the use of patient registries for patient follow-up [60][61][62][63]. We did not find studies exploring the service delivery strategy of decentralizing hypertension care services closer to the community.
Financing of health systems is another critical aspect of hypertension and other health services' accessibility and utilization. Studies in the current review have shown that addressing the cost-related barriers to care can contribute to helping patients with hypertension achieve better outcomes-the subsidization of health insurance premiums. Universal health coverage through government-subsidized insurance premiums has been advocated as a solution to prevent catastrophic spending on healthcare services and associated poor health outcomes [64][65][66]. However, financing universal health coverage requires political buy-in and collaboration across sectors, local and international [65].
While leadership and governance are central to the success of any endeavor to improve the quality of care, their role and impact in advancing hypertension care in SSA are not widely researched, and the few existing studies are predominantly of poor quality [67]. Thornton highlighted the critical values of leadership commitment, willingness to fund care, strategic and creative local and foreign partnerships, and evidence-based guidelines as the key reasons why Botswana surpassed the United Nations' HIV management goals of 95% awareness, 95% on treatment, and 95% [55]. A 3-year campaign mobilization on the role of clinical leaders in hypertension management at various health systems in the United States achieved the goal of 80% BP control within seven months [68]. A scoping review of interventions to strengthen the health professionals' leadership in SSA found that the opportunities for leadership development in SSA are scarce, and those available are of poor quality and lack a consistent evaluation framework [67]. There is a need for more studies on strengthening leadership in healthcare and exploring its impact on health outcomes, including hypertension in SSA.
We found that interventions addressing multiple health system factors were more likely to report better hypertension outcomes than isolated investment in a single health system component. Health systems in most SSA countries, especially rural areas, are often frail in the multiple health system factors [69]. The inventions aiming to improve how those health systems manage a health condition such as hypertension should first assess health systems' readiness to identify the areas of focus for those interventions.
As the burden of hypertension increases globally, the investment required by health systems to manage hypertension is rising. Hypertension is significantly associated with adverse outcomes of Coronavirus Disease 2019 (COVID-19), the ongoing pandemic ravaging the entire world's health systems [70,71]. Studies reported that hypertensive patients had almost three times the odds of mortality compared to people without hypertension [70]. The long-term post-COVID symptoms haunt the patients with hypertension who survive COVID-19 more than the general population [72]. For instance, patients with hypertension are twice as likely to have migraine-like headaches and 68% higher odds of poor sleep than people without hypertension [72]. Apart from the COVID-19 rationale, under the Sustainable Development Goal (SDG) 3 (Ensure healthy lives and promote well-being for all at all ages), target 3.4 aims to reduce by one-third the premature mortality from non-communicable diseases [73]. The management of hypertension, a significant risk factor for cardiovascular diseases, is a step closer to achieving target 3.4 of SDG 3.
Standard tools for exploring the health system determinants for specific diseases are scarce in the realm of hypertension care in Africa. There is a dire need for psychometric tools to explore health system readiness to provide quality hypertension care. The availability of those tools would open doors for researchers interested in hypertension care to gather quality data on health system determinants and render the evidence to policymakers to develop policies directed at shortfalls in care delivery to improve the health outcomes of patients with hypertension.
Future studies should investigate the different aspects of hypertension service delivery, especially interventions that make service accessible, the role of leadership and governance, the latest methods of health information system management including the use of electronic medical records for patient follow up, as well as multi-level approaches (i.e., individual, community, provider, health system) in the improvement of hypertension care. To improve the quality of the studies, the quality improvement projects aimed at testing the interventions in clinical settings and evaluative projects aimed at generating knowledge will have to be rigorously guided by the science of study design. Since healthcare settings are ever dynamic with many interconnected components, the appropriate design has to be carefully identified allowing the balance between controlling the allocation of the interventions with prevention of contamination and bias and the pragmatism of the project in the research setting [74,75]. The procedures and reasons for omitting standard practices of study design and implementation will, however, have to be acknowledged and adequately described. Additionally, while the current review explored interventions conducted in SSA, most studies were conducted in three countries (Cameroon, Kenya, Nigeria, and South Africa). Future studies should explore health systems interventions for hypertension care in other countries of SSA. Such studies could inform the much-needed local guidelines for hypertension care and patient follow-up.

Strengths and limitations
The limitation of the current review is that we conducted the literature search in English. Even though we reviewed studies published in both English and French, the English search terms, could limit our ability to identify studies published in other languages. We were unable to explore the isolated effect of individual health system factors interventions, because many system interventions were delivered in a bundled approach. However, this review offers valuable insights as the first to explore the health systems interventions on hypertension care in SSA, applied rigorous methods to critique the quality of the studies, and reviewed the interventions using the WHO health systems framework [22].

Conclusion
The literature exploring health system interventions for hypertension management in SSA is limited in volume and quality. The combination of multiple health system interventions was likely to result in better hypertension outcomes. More rigorously designed studies addressing the different aspects of the health systems and their impact on hypertension outcomes, especially service delivery, health information management, and leadership and management, are needed in SSA to inform practical hypertension control efforts.